[DOC] - Create placeholder documentation

[andrewfulton9]

Preliminary Checks

• This issue is not a question, feature request, RFC, or anything other than a bug report. Please post those things in GitHub Discussions: https://github.com/nebari-dev/nebari/discussions

Summary

Add placeholder docs and framework for building and deploying:

• github workflow that builds in pr and deploys to gh pages on merge to main
• docusaurus/typescript/npm configs
• readme.md on tools, how to build, serve ect
• docs/introduction page
• relevant styling assets
• update .gitignore